In 1834 Robert Bunsen discovered that arsenious oxide, a highly toxic material, could be rendered innocuous by contacting with iron oxide. The mechanism involved in this adsorption has been studied extensively as summarized in Gallegos-Garcia et al. (Mineral Processing & Extractive Metall. Rev. 33: 301-315, 2012). Various forms of iron oxides, such as hematite (Fe2O3), are reported to share structural oxygen atoms with arsenious oxides in angelellite-like local clusters.
These principles have been converted into industrial methods for the treatment of anthropogenic sources of arsenic such as flue dusts from smelters or naturally occurring contamination of water tables. The end products after adsorption of arsenic on hematite are found to be able to not release the arsenic, either trivalent or pentavalent as per standard acetic acid leaching procedure: EPA 1311 Toxicity Characteristic Leaching Procedure (TCLP). However, extreme pH condition or mechanical attrition can disperse this fixed arsenic in the environment.
Therefore, it has appeared desirable to complete this capture of arsenic by hematite by grouping the particulates obtained after adsorption into a macroscopic glass structure. Sequestration of arsenic by glass formation is a known procedure (U.S. Pat. No. 8,998,790). It was made possible by the thermal stability of calcium arsenate at a temperature where glass forming elements can lead to stable and homogeneous glass.
There is still a need in the art for a method and a composition for sequestration of arsenic.
The present description refers to a number of documents, the content of which is herein incorporated by reference in their entirety.